ISO 8780-6:1990

Overview - ISO 8780-6:1990 (Pigments and extenders - Triple-roll mill dispersion)

ISO 8780-6:1990 specifies a laboratory method for dispersing pigments and extenders using a triple-roll mill to assess dispersion characteristics. The procedure is intended for high‑viscosity mill bases and is used together with the assessment methods in ISO 8781 (tinting strength, fineness of grind, gloss). Results help predict how a pigment will behave on corresponding production machinery but are not directly comparable with dispersibility results from other dispersion methods.

Key topics and technical requirements

• Scope: Method for dispersion using a triple‑roll mill to evaluate pigments/extenders in high‑viscosity mill bases.
• Equipment: Triple‑roll mill with temperature control and mixing unit; roll diameter about 150 mm (other sizes must be agreed and recorded); roll length 200–300 mm; roll speed 150–200 r/min; transmission ratios ~1 : (2.5 to 3) : (5 to 6).
• Roll contact force: Expressed as line pressure, reproducible up to 80 cN/mm roll length (convertible to pressure per mill design); avoid metal‑to‑metal contact.
• Sample and conditions:
  • Minimum mill base mass for specified apparatus: 50 g.
  • Temperature control: ±1 °C within 20 °C to 60 °C.
  • Pre‑mixing: thorough spatula mixing (about 2 min for 50 g typical) or by agreed alternative (e.g., impeller mill).
• Pigment concentrations (typical examples):
  • Low binder demand: 65% pigment (m/m).
  • Medium binder demand: 40% pigment (m/m).
  • High binder demand: 25% pigment (m/m).
• Procedure details: Pre‑heat rolls, set contact forces progressively, collect mill base from the apron, discard material running off roll sides, and stabilize test portions if required.
• Reporting: Include identification, reference to ISO 8780‑6, binder system details, mill base composition and temperature, pre‑mixing/dispersion conditions, stabilization, deviations, and test dates.

Applications and users

• Paint, coatings and ink manufacturers assessing pigment dispersibility and likely behavior on production triple‑roll mills.
• Quality control and R&D labs comparing test pigments against agreed reference pigments using a standardized high‑viscosity mill base and binder system.
• Process engineers correlating lab dispersion performance with production machinery behavior.
• Useful when evaluating tinting strength, fineness of grind, or gloss following ISO 8781 assessment methods.

Related standards

• ISO 8780 (all parts 1–5 and 6)
• ISO 8781 (assessment methods: tinting strength, fineness of grind, gloss)
• ISO 787‑24 (relative tinting strength / white pigment paste reference)
• ISO 842 (sampling)
• ISO 1524 (fineness of grind)

Keywords: ISO 8780-6:1990, triple-roll mill, pigment dispersion, dispersibility, mill base, binder system, paint industry, fineness of grind, tinting strength.